biochem Flashcards
Water forms Hydrogen Bonds with?
Sulfur, oxygen and nitrogen atom (SON)
Define amphoteric and amphipathic
Amphoteric - acts as both an acid and a base, Amphipathic - has hydrophilic an hydrophobic parts
What is the normal pH?
7.35 - 7.45
DKA Criteria
Diabetic, Ketosis (+) urine ketones, ABG that documents acidosis
Important physiologic buffers
Bicarbonate - extracellular, Proteins - intracellular
Distinct versions of a given enzyme that catalyze the same reactions
Isozymes
Enzymes that catalyze the joining together of 2 molecules coupled to the hydrolysis of ATP
Ligases
Refers to the enzyme and its co-factor
Holoenzyme
True or false: enzymes that follow the Michaelis-Menten equation have a hyperbolic curve
True - equation describes how reaction velocity varies with substrate concentration
Reversal of competitive and non competitive inhibitors
Competitive - increase substrate, Noncompetitive - increase enzyme
Vmax change during inhibition
Competitive - not changed, Non competitive- lowered
What enzyme markers would best confirm a re-infarct?
CK-MB
Can be used to predict whether a reaction is spontaneous or not
Change in free energy
Equation of Change in Free Energy
Energy currency of the cell. It’s hydrolysis yields a large
ATP,
Differentiate oxygen phosphorylation from substrate level phosphorylation
Oxidative phosphorylation - mitochondria, oxygen needed. Substrate level phosphorylation - cytoplasm and mitochondria, oxygen not needed
Where does the ETC occur?
Inner mitochondrial membrane
2 electron carriers in the ETC
NAD+ from Vit B3 (thiacin), FAD from Vit B2 (riboflavin)
Only non-protein part of the ETC
Coenzyme Q - lipid, ubiquinone
Final electron acceptor in ETC
Oxygen
Protons re enter the mitochondrial matrix in ETC through?
Complex V - results in synthesis of ATP, contains ATP Synthase
2 components of ATP Synthase
F0 - channel where protons pass through, F1 - generates ATP from ADP and Pi
Names of the complexes in the ETC
I-NADH dehydrogenase, II-Succinate dehydrogenase, III-Ubiquinol, IV-Cytochrome oxidase
ETC inhibitor: Dimercaprol
Complex III - antidote to lead poisoning
ETC inhibitors: Barbiturates
Complex I
ETC inhibitors: cyanide
Complex IV
ETC inhibitors: carbon monoxide
Complex IV
ETC inhibitors: malonate
Complex II
Antidote to cyanide poisoning (bitter almond breath)
Amyl nitrite
Neonates rely on this protein to produce heat and prevent hypothermia
Thermogenin - through uncoupling
Macrolide that acts as an ATP Synthase inhibitor
Oligomycin
3 reactive oxygen species
Superoxide (O2), hydrogen peroxide (H2O2), and hydroxyl radical (OH)
Defenses against ROS accumulation
Catalase, Peroxidase, Superoxide dismutase
Glucose + Glucose
Maltose
Glucose + Galactose
Lactose
Glucose + Fructose
Sucrose
Mitochondrial disease affecting complex I
MELAS - mitochondrial encephalopthy, lactic acidosis, stroke like episodes
Mitochondrial disease affecting complex III
Leber’s hereditary optic neuropathy
Sugar units (disaccharides) are linked by?
Glycosidic bonds
Differentiate a proteoglycan from a glycoprotein
Proteoglycan (carbs>proteins), Glycoprotein (protein>carbs)
Polysaccharide found in cereals, potatoes, nuts
Starch
Polysaccharide of fructose, can be used to check renal function
Inulin
Compounds that have the same chemical formula but different structures
Isomers
Compounds that differ in configuration around only one specific carbon atom
Epimers
Sugar form that is more common in enantiomers
D-sugar
2 forms of anomers
Fischer projection (linear), and Haworth projection (ring)
Enzyme that can hydrolyze complex carbohydrates to disaccharides
Pancreatic amylase
Predominant transporter of glucose and galactose
SGLT 1 - via secondary active transport
Transporter for glucose, galactose and fructose
GLUT 5 - via facilitated diffusion
Transporter for all sugars
GLUT 2 - via facilitated diffusion
2nd messenger of insulin
Tyrosine kinase
Protein kinase G acts on what pathway?
cGMP
Substrate used in the inositol triphosphate system
Phosphatidylinositol
Enzyme that converts ATP to cAMP
Adenylate cyclase
Enzyme that degrades cAMP to 5 AMP
cAMP phosphodiesterase
GLUT transporter whose function is insulin stimulated uptake of glucose
GLUT 4 - found in muscle and adipose tissue
GLUT transported whose function is absorption of glucose in the lumen
GLUT 5 - in the small intestine
Where does glycolysis occur?
Cytoplasm of all cells
Rate limiting step of Glycolysis
Fructose 6 phosphate ? fructose 1,6 bisphosphate (E: PFK 1)
End products of anaerobic and aerobic glycolysis
Lactate (anaerobic), Pyruvate (aerobic)
Isozymes that catalyze the phosphorylation of glucose
Hexokinase, Glucokinase
Allosteric activator of PFK 1
PFK 2
Enzyme that catalyzes the formation of pyruvate
Pyruvate kinase
Malate aspartate shuttle is found in the?
Liver, kidney and heart (1 NADH = 3ATP)
Glycerol phosphate shuttle is found in the?
Skeletal muscle and brain (1NADH = 2 ATP)
What organs convert pyruvate to lactate?
RBCs, lens and cornea of eye, kidney medulla, testes, WBC
Most common enzyme defect in glycolysis?
Pyruvate Kinase Deficiency - presentation is chronic hemolytic anemia
Central molecule from pyruvate that enters the Kreb’s Cycle
Acetyl CoA
Congenital lactic acidosis. X linked dominant disease
Pyruvate dehydrogenase deficiency - treat with a ketogenic diet
Final common pathway for the aerobic oxidation of all nutrients
TCA/Kreb’s Cycle/Citric Acid Cycle
Rate limiting step in the Kreb’s Cycle
Isocitrate ? alpha ketoglutarate (E: isocitrate dehydrogenase)
Fluoroacetate (rat poison) inhibits what step in the Kreb’s Cycle?
Citrate ? Isocitrate (E: Aconitase)
Arsenite inhibits what step in the Kreb’s Cycle?
Alpha ketoglutarate ? Succinyl CoA (E: alpha ketoglutarate dehydrogenase)
Where does gluconeogenesis occur?
90 % liver, 10% kidney
Rate limiting step in Gluconeogenesis
Fructose 1,6 bisphosphate ? Fructose 6 phosphate (E: fructose 1,6 bisphosphatase)
Cycle that converts lactate to glucose via hepatic gluconeogenesis
Cori cycle - energy expense of 4 ATPs
Carboxylases require this as a co-factor
Biotin
Rate limiting step in the Cori Cycle
Fructose 1,6 bisphosphate ? fructose 6 phosphate (E: fructose 1, 6 bisphosphatase)
What are the dual functions of fructose 2,6 bisphosphate
Promotes glycolysis and inhibits gluconeogenesis
What enzyme does muscle lack to produce glucose?
Glucose 6 phosphatase
Blood concentration of glucose resulting to glucosuria
> 180mg/dL
Where is glycogen stored?
Liver and muscle
Rate limiting step in Glycogenesis
Elongation of glycogen - addition of alpha 1?4 bonds (E: glycogen synthase)
Rate limiting step of Glycogenolysis
Breaking of alpha (1?4) bonds (E: glycogen phosphorylase)
Enzyme used in the lysosomal degradation of glycogen
Alpha(1?4) glucosidase or acid maltase
Glucose 6 phosphatase deficiency (Glycogen storage disease)
Type I: Von Gierke’s - hepatomegaly, hypoglycemia, lactic acidosis
Acid maltase deficiency (Glycogen storage disease)
Type II: Pompe’s - cardiomegaly and HF
Deficiency in debranching enzyme (Glycogen storage disease)
Type III: Cori’s disease - milder form of type I
Deficiency in skeletal muscle glycogen phosphorylase (Glycogen storage disease)
Type V: McArdle’s disease
True or false: Hexokinase has a greater affinity for glucose
TRUE
Enzyme that phosphorylates galactose
Galactose ? Galactose 1 phosphate (E: Galactokinase or Hexokinase)
Enzyme deficient in Classic Galactosemia
Galactose 1-P uridyltransferase
Autosomal recessive disorder where there is an accumulation of Galactitol
Classic Galactosemia - cataracts, hepatosplenomegaly and mental retardation
The activated form of galactose
UDP-galactose
Differentiate Aldolase A from Aldolase B
Aldolase A - for glycolysis, Aldolase B - for fructose metabolism
Benign condition, only presentation is fructose in blood and urine
Essential fructosuria - deficiency in fructokinase
Autosomal recessive condition where there is a deficiency of Aldolase B
Fructose intolerance - increased fructose 1 P, dec phosphate/glycogenolysis/gluconeogenesis
Product responsible for the complications of DM
Sorbitol - attracts water
Enzyme found in seminal vesicles that converts sorbitol to fructose
Sorbitol dehydrogenase
Rate limiting step on the Pentose Phosphate Pathway
Glucose 6 phosphate ? 6 Phosphogluconate (E: Glucose 6 P dehydrogenase)
Vitamin required as a co-factor in Transketolases
Vit B1 (Thiamine) - part of the reversible non oxidative phase 2 of Pentose phosphate pathway
Product of the Pentose Phosphate Pathway that is used in the synthesis of nucleotides
Ribose 5 phosphate
Most common disease producing enzyme abnormality in humans
G6PD Deficiency - dec NADPH in RBCs and dec activity of glutathione
Altered Hgb that precipitates within RBCs in G6PD Deficiency
Heinz bodies
NADPH oxidase deficiency that leads to increased incidence of infections with Catalase (+) bacteria
Chronic Granulomatous Disease
What kind of fatty acids are associated with increased risk of cardiovascular disease?
Trans and saturated fatty acids
Essential FAs that cannot be synthesized in the body
Linoleic acid, Linolenic acid
Precursor of arachidonic acid that is essential in prostaglandin synthesis
Linoleic acid - essential FA
Rate limiting step in FA Synthesis
Acetyl CoA + ATP ? Malonyl CoA (E: Acetyl CoA carboxylase)
Transfer of Acetyl CoA from the mitochondria to the cytoplasm occurs through a?
Citrate shuttle
Where is Acetyl CoA produced?
Mitochondrial matrix
Main storage form of fatty acids
Triacylglycerols
Enzyme that hydrolyzes TAGs to yield FFAs and glycerol
Hormone sensitive lipase
Rate limiting step in Beta Oxidation of FAs
Fatty acyl CoA + Carnitine ? fatty acyl carnitine + CoA (E: carnitine acyltransferase)
Long chain FAs is brought to the inner mitochondrial membrane for Beta oxidation of FAs through?
Carnitine shuttle
Organelle that oxidizes very long chain FAs (20-22 carbons)
Peroxisomes
Can manifest as Sudden Infant Death Syndrome due to decreased FA oxidation
Medium chain fatty acyl CoA dehydrogenase - no ATP to support gluconeogenesis, treat with IV glucose
Toxin in Jamaican Vomiting Sickness
Hypoglycin - unripe fruit of Akee tree
Neurologic disorder due to accumulation of Phytanic acid that blocks beta oxidation
Refsum’s Disease
Rare inherited absence of peroxisomes in all tissues
Zellweger’s Syndrome - liver dysfunction, mental retardation, craniofacial dysmorphism
Where does ketogenesis occur?
Liver mitochondria
Product of ketogenesis that is not used as fuel
Acetone
Rate limiting step in ketogenesis
Acetoacetyl CoA + acetyl CoA ? HMG CoA (E: HMG CoA synthase)
Liver cannot convert acetoacetate to acetyl CoA because it lacks which enzyme?
Succinyl-CoA acetoacetyl-CoA transferase (thiophorase)
Urine test for ketones
Nitroprusside test
Where dows cholesterol synthesis occur?
Cytosol and smooth ER of liver and intestines
Rate limiting step in cholesterol synthesis
HMG CoA ? Mevalonate (E: HMG CoA reductase)
Intermediate in Cholesterol synthesis that is used for synthesis of Coenzyme Q for the ETC
Farnesyl pyrophosphate
How does acetyl CoA reach the cytosol for cholesterol biosynthesis?
Citrate shuttle
Primary means of excreting cholesterol
Bile salts (bile acid + glycine or taurine)
Where does enterohepatic circulation occur?
95% of bile is reabsorbed in terminal ileum
Mother hormone in steroid hormone synthesis
ACTH
Rate limiting step in steroid hormone synthesis
Cholesterol ? Pregnenolone (E: desmolase)
Protein secreted by enterocytes to make lipids more soluble in blood
Apoprotein B 48
Enzyme that breaks down triglycerides to FA and glycerol
Lipoprotein lipase
Apoprotein in chylomicron that activates lipoprotein lipase
Apo C-II
Apoprotein in VLDL secreted by the liver
Apo B-100
Apoprotein in HDL that activates Lecithin Cholesterol Acyltransferase (LCAT) to produce cholesterol esters
Apo A-1
Picks up cholesterol from HDL to become LDL
IDL
Delivers cholesterol into cells using Apo B 100
LDL
Picks up cholesterol accumulating in blood vessels and delivers it to liver via Scavenger Receptor (SR-B1)
HDL
Deficient in Abetalipoproteinemia resulting to intestinal malabsorption
Apo B 48 and Apo B 100 - no chylomicron, no VLDL/LDL
Deficiency in lipoprotein lipase leading to high VLDL and chylomicron with low LDL and HDL
Type I Familial lipoprotein lipase - xanthomas and pancreatitis
Deficiency in LDL receptors leading to high LDL
Type II Familial hypercholesterolemia - risk for atherosclerosis and coronary heart disease
Phospholipid important in nervous transmission as Acetylcholine
Phosphatidylcholine - most abundant phospholipid
Phospholipid that is a major component of lung surfactant
Dipalmitoylphosphatidylcholine (DPPC) or lecithin
Phospholipid that is the source of 2nd messengers
Phosphatidylinositol
Phospholipid found only in mitochondria an is essential for its function
Cardiolipin
Cardiolipin is antigenic. It reacts with antibodies produced?
Treponema pallidum (syphylis)
Only significant sphingolipid in humans, important part of myelin sheath
Sphingomyelin
Deficiency in Hexosaminidase A
Tay-Sach’s disease - cherry red macula, MR and hypotonia
Deficiency in alpha Galactosidase
Fabry’s disease - X linked recessive, rash, renal failure
Deficiency in beta glucosidase
Gaucher’s disease - hepatosplenomegaly and erosion of long bones
Deficiency in sphingomyelinase
Niemann-Pick disease resulting to hepatosplenomegaly
Dietary precursor of Eicosanoids
Linoleic acid
Immediate precursor of Eicosanoids
Arachidonic acid
Eicosanoid produced by blood vessel walls
Prostacyclin - inhibits platelet aggregation
Set of all proteins expressed by an individual cell at a particular time
Proteome
Amino Acid that accumulated in Maple syrup disease
Branched chain AAs - valine, leucine, isoleucine
AA with the smallest side chain that is used in the first step of heme synthesis
Glycine - major inhibitory neurotransmitter in the spinal cord
Enzyme deficient in PKU leading to an increase in amounts of phenylalanine
Phenylalanine hydroxylase
AA that is the precursor of niacin, serotonin and melatonin
Tryptophan - has the largest side chain
Covalent disulfide bonds combine 2 cysteines to form?
Cystine - found in keratin
AA that is a precursor of thyroxine and melanin
Tyrosine
Sited for O-linked glycosylation in Golgi apparatus
Serine and Threonine
Site for N-linked glycosylation in ER
Asparagine
AA that is a major carrier of nitrogen to the liver from peripheral tissues
Glutamine
AA that is the major precursor for GABA and glutathione
Glutamate
AA that is the precursor of histamine
Histidine
AA that is the precursor of creatinine, urea and NO
Arginine
Configuration of all AAs in proteins
L-configuration
Attach alpha amino group of one AA to the alpha carbonyl group of another
Peptide bonds -trans configuration
Secondary structures of proteins are stabilized by?
Hydrogen bonds
Most common protein secondary structure
Alpha helix - R handed spiral with polypeptide backbone core
3 dimensional shape of a protein that have a specific function
Tertiary structure - stabilized by disulfide bonds, hydrogen bonds and ionic bonds
Structure of proteins consisting of more than 1 polypeptide chain
Quaternary structure - non covalent bonds
What are the normal and abnormal proteins in Prion Disease?
PrPc (normal-rich in alpha helices), PrPsc (abnormal-rich in beta sheets)
Complex of protoporphyrin IX and ferrous iron
Heme - reversibly binds oxygen in myoglobin and hemoglobin
Major transported of CO2 in the blood
Bicarbonate (75%)
Symptoms of chocolate cyanosis, headache and dyspnea
Methemoglobinemia - increased affinity of ferric for cyanide (stops complex IV of ETC)
Treatment for carboxyhemoglobin
Hb is cherry pink in color, treat with 100% O2 to displace carbon monoxide
Most common mutation in hereditary spherocytosis
Ankyrin - splenectomy for symptomatic patients
Point mutation in both genes coding for the beta chain that results in a valine rather than a glutamate
Sickle cell disease - homozygous recessive disorder
Disease with a single AA substitution in the 6th position of the beta globin chain where lysine is substituted for glutamate
Hemoglobin C disease - mild hemolytic anemia
When do symptoms of anemia appear in Alpha and Beta thalassemia
Alpha-at birth, Beta-after birth
Most abundant protein in the body
Collagen -triple helix stabilized by hydrogen bonds
Disease with hyperextensible skin, bleeding tendencies, hypermobile joints and increased risk for berry aneurysms
Ehlers-Danlos Syndrome - Type III collagen
Disease: multiple fractures, blue sclerae, hearing loss, and dental imperfections
Osteogenesis imperfecta or Brittle Bone Syndrome - collagen type I
Vit C deficiency leads to decreased cross linking of collagen fibers
Scurvy - sore spongy gums, loose teeth, poor wound healing
Syndrome: hematuria, ESRD, sensorineural hearing loss
Alport syndrome - collagen type IV
Kinky hair and growth retardation due to a deficiency in copper required by Lysyl oxidase
Menke’s Syndrome
Deficiency in Type VII collagen
Epidermolysis Bullosa
Marfan syndrome is autosomal dominant and presents with a mutation in this gene
Fibrillin gene
Most powerful pancreatic enzyme that digests proteins
Trypsin
Major disposal form of nitrogen
Urea
Vitamin needed for Transamination (removal of Nitrogen)
Vitamin B6 - pyridoxal phosphate
Enzyme that oxidizes and deaminates glutamate to yield free ammonia that is used to make urea
Glutamate dehydrogenase
Enzyme: Glutamate + Ammonia ? Glutamine
Glutamine Synthetase
Enzyme: Pyruvate + Glutamate ? Alanine + Alpha Ketoglutarate
ALT or SGPT
Pathway for removal of nitrogenous waste products in the body
Urea cycle - happens only in the liver
Rate limiting step of Urea Cycle
CO2 + NH3 ? Carbamoyl phosphate (E: Carbamoyl phosphate synthetase I)
Only product in the Urea Cycle that can penetrate the mitochondrial membrane
Citrulline
Disease: hyperammonemia, elevated glutamine and decreased BUN
Hereditary hyperammonemia - lethargy, vomitig, hyperventilation, convulsions, coma